In the tree care industry or field of arboriculture, the treatment of trees with therapeutic and prophylactic chemicals is commonly used to control tree disease and insect problems, as well as for the purpose of tree fertilization and growth control. The most environmentally sound and economically feasible approach to such chemical applications in trees is to inject, infuse, or implant the chemical directly into the tree. Various techniques are currently being used for both commercial and research application of the injection, infusion, and implantation methods. All of these methods require the physical wounding of the tree, usually by drilling a hole into the trunk, and the subsequent, inadvertent introduction of air into the xylem or water conducting elements of the tree.
The concept of injecting trees, and plants in general, is not a new one, with a report of tree injection by Leonardo da Vinci in the 12th century. In more modern times the practice of injecting trees with therapeutic and prophylactic chemicals has become quite common. In the tree care and agricultural industries there exists a wide interest in tree injection systems and methods, and numerous professional and scientific journals are common forums for methodology and applications of such systems.
Prior art "tree Injection" in its widest sense can include a wide range of methodology and purposes relating to the injection, infusion, or implantation of chemicals into trees. Injection, in its truest sense refers to the "pressure injection" or the introduction of chemicals under pressure greater than atmospheric pressure. Infusion has been used to refer to a more passive introduction of chemicals into trees; that is to inject by the force of gravity and atmospheric pressure without additional applied pressure. Implantation, is the insertion of a chemical, in solid form, into a holed drilled in the tree.
The most common practice or technique used to inject trees is to drill a hole into the trunk of the tree and then attach one or more adaptors through which the chemical can be introduced into the tree by injection or infusion. Injections are also made through drill wounds in the root and root-trunk flare area of trees. Injection wounds have also been made using a "shallow-pit" technique, and by an "insertion-tool technique". All of these injection methods employ wounding of the tree and subsequent introduction of air into the water conduction system of the tree.
The physiology of water movement in trees is well presented in the literature, and the adverse effect which trunk wounding and embolization has on the water conduction in trees is known. The inadvertent introduction of air into the tree's water conduction system, during tree injections, has long been recognized as an impairment to systemic distribution of chemicals in diseased trees, and limited, systemic chemical distribution is widely considered to be the greatest hindrance to effective disease control in trees. The need to improve systemic chemical distribution has been recognized and it has been suggested that the removal of air from injection wounds by vacuum infiltration techniques as one method that has reasonable potential to improve systemic distribution of injected chemicals in trees. To date, there is no evidence of commercial or research applications of such techniques in the professional and scientific literature.
In normal tree function, water is supplied to the leaves by the roots through the transpirational stream which is comprised of the xylem or water conducting elements of the trunk and branches. The mechanism for water movement is through a tension or negative pressure system based on the molecular adhesion of water molecules. As water is evaporated from the leaf surfaces, the tension created by molecular bonds pulls water molecules from the transpirational stream to replace them. This system pulls water, molecule by molecule from the root system to the leaves creating a tension or negative pressure gradient. This transpirational pull can create tensions within the conducting elements as low as -30 atmospheres; with -5 to -20 atmospheres being common during the summer months. As is known to those skilled in the art, these pressure measurements correspond to the values of positive pressures needed to cause reverse transpiration of water. That is, the tension is the negative of the value of pressure needed to be applied to the leaf to urge water through a cut portion of the stem. For example, a tension of -5 atmospheres is obtained in a leaf which requires 5 atmospheres of positive pressure to urge a drop of water from its stem.
The systemic tree treatment systems and methods currently in commercial and research use cause the introduction of air into the transpirational stream of the tree, thereby embolizing the conducting elements and breaking the water columns necessary for systemic movement of compounds within a tree. In effect, the methods employed by these known systems disrupt and render dysfunctional the very water-conducting elements necessary for the must efficient and effective systemic movement within trees.